Air cargo is a vital component of many international logistic networks, essential to managing and controlling the flow of goods and other resources from the source of production to the marketplace. For air cargo transportation, as well passenger aircraft and cargo aircraft are used. A passenger aircraft comprises a lower deck for the air cargo which is available under the passenger's main deck. A pure cargo aircraft (also known as freight aircraft, freighter, airlifter, or cargo jet) is an aircraft that is designed or converted for the carriage of goods, rather than for passengers. In cargo aircraft the main deck as well as the lower deck is used to carry cargo.
In modern cargo aircraft, cargo may be loaded through hinged cargo doors located in a side of the fuselage. For loading the cargo aircraft, specifically designed ULDs (unit load devices) are typically used. ULDs are containers or pallets which are used to load luggage, freight and other products into the cargo compartment of an aircraft. It allows a large quantity of cargo to be bundled into a single unit. Since this leads to fewer units to load, it saves ground crew's time and effort.
During loading, the ULDs are transferred into the fuselage through the hinged cargo door and are then maneuvered on the cargo deck which for this purpose comprises a cargo loading system. The cargo loading system typically consists of a plurality of uni-directional or multi-directional transfer supports to ease the passage of ULDs over the surface of the cargo deck and into a final stowed position where they are secured to the cargo deck against movements by a number of either fixed or relocatable restraints. The function of these restraints, commonly referred to as end stop devices, is to prevent movement of the cargo during operation, i.e. during takeoff, flight and landing. During operation, the ULDs are resting against these end stop devices.
At the fore portion of the cargo hold of an aircraft, cargo needs to be restrained from moving forward during deceleration maneuvers of the aircraft. Such cargo restraining barriers, sometimes referred to as buffer stop assemblies, roll and lock into the forward end of an aircraft cargo hold equipped with a roller restraint cargo system. Document U.S. Pat. No. 6,568,636 B2 for example discloses a buffer stop assembly for engagement within cargo aircraft to resist cargo movement. The buffer stop assembly comprises a horizontal member selectively engageable to the aircraft and a substantially vertical member resistant to movement by aircraft cargo, which members are mounted to each other. The vertical member can be moved between an extended position and a transport position overlying the horizontal member.
Typical buffer stop assemblies, such as the one from document U.S. Pat. No. 6,568,636 B2, are movable and fixable along corresponding seat track profiles or rails which are provided in the cargo deck surface. During operation, the complete cargo within the cargo deck is typically secured by the buffer stop assembly which consequently has to take up high forces and loads. Therefore, a specific requirement of buffer stop assemblies is their capability to take very high loads without breaking. Commonly known buffer stop assemblies thus have a rather massive construction. Massive construction, however, means additional weight and costs.
Additionally, the document U.S. Pat. No. 6,568,636 B2 discloses a center and vertical restraint system (CVRS) to enable the cargo hold to load and transport multiple adjacent rows of cargo containers. The CVRS is connected to existing tie down rings in the middle and along the cargo hold via studs. Document US 2013/0334367 A1 discloses an aircraft cargo handling system having a pair of load restraining rail assemblies, each of which has a shaft assembly running substantially parallel to the longitudinal axis of the aircraft. The shaft assembly has a plurality of lock pawls, each of which comprises a body having a cylindrical pallet-engaging surface.